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PubMedDate not supplied

[The structure of the cortical-subcortical relationships of the cerebral electrical processes during a motor polarization dominant].

Under conditions of rabbit chronic experiments, it was shown by means of the spectral-coherence analysis that the motor polarization dominant formed by the application of DC anode to the sensorimotor cortex produced a novel structure of the intercentral relations between electrical processes not only in the ipsi-, but in the contralateral brain hemisphere. A certain "isolation" of the primary focus was observed in the cortex of the "dominant" hemisphere, which was manifested in a decrease in its delta-range coherent relations with the other cortical areas. At the dominant optimum (in interstimulus intervals), an interhemispheric asymmetry in the EEG coherence spectra was observed in the delta band between the sensorimotor cortical areas, ventroposterolateral thalamic nuclei, and CA3 fields of the dorsal hippocampi. The asymmetry increased during the testing auditory stimulation. Development of the alpha- and beta-band interhemispheric asymmetry in the structures in question coincided with realization of the motor "dominant" reaction and was suggested to be associated with movement organization.

Animals↗
PubMed1996

Long-term effects of neonatal ischemic-hypoxic brain injury on sensorimotor and locomotor tasks in rats.

Perinatal ischemia and/or hypoxia in humans are major risk factors for neurologic injury that often manifest as sensorimotor and locomotor deficits throughout development and into maturity. In these studies, we utilized an established model of neonatal ischemic-hypoxia that creates unilateral striatal, cortical, and hippocampal damage (Rice III, J.E., Vanucci, R.C. and Brierley, J.B., Ann. Neurol., 9 (1981) 131-141) to investigate sensorimotor and locomotor deficits in these animals during development and as adults. Sensorimotor deficits were examined by measuring the amount of time that the animals were able to remain on a rotating treadmill. Locomotor abnormalities were assessed by measuring apomorphine-induced rotational asymmetry. Following the neonatal ischemic-hypoxic episode, at 3-9 weeks of age, animals were not able to remain on the treadmill as long as their normal littermate controls. In addition, these animals demonstrated an abnormal, ipsiversive rotational asymmetry in response to systemic administration of apomorphine. When these animals reached adulthood, the degree of atrophy in specific regions of the damaged hemisphere was quantified using measurements of cross-sectional area. The mean cross-sectional area of the striatum was decreased by 29%, the sensorimotor cortex area by 26%, and the dorsal hippocampus cross-sectional area was approximately 6% of its normal size. These data suggest that this rodent model of neonatal ischemic-hypoxic brain injury results in cerebral atrophy and long-lasting sensorimotor and locomotor deficits. These particular behavioral tasks may be used in future studies to assess locomotor and sensorimotor deficits following neonatal ischemic-hypoxic brain injury.

Animals↗
PubMed1987

Structural changes in caudate nucleus, cerebral cortex and hippocampus induced by morphine. Light microscopy study.

Intraperitoneal chronic morphine administration to rats produced structural alterations in nerve cells of caudate nucleus, cerebral cortex and hippocampus. All areas studied showed increased alterations related to time elapsed between last morphine injection and fixation of tissue samples. Lesions mainly consisted in vacuolar degeneration of nerve cells. The most extense and intense lesions were observed in hippocampus. Sensorimotor cortex and caudate nucleus showed focal damage. Neurocytotoxic effect of morphine appears to be unrelated to the opiate receptor density in brain areas, and the brain regions susceptible to that effect appears to be different from brain areas related to adaptation to morphine. Effect of morphine on integrity and function of nerve cells mitochondria, interfering with energy production could play an important role in the pathogenesis of neuronal lesions.

Animals↗
PubMed2004

alpha2-Adrenergic receptor-mediated modulation of calcium current in neocortical pyramidal neurons.

Noradrenergic projections to the cortex modulate a variety of cortical activities and calcium channels are one likely target for such modulation. We used the whole-cell patch-clamp technique to study noradrenergic modulation of barium currents in acutely dissociated pyramidal neurons from rat sensorimotor cortex. Extracellular application of specific agonists and antagonists revealed that norepinephrine (NE) reduced Ca2+ current. A major component of this modulation was due to activation of alpha2 receptors. Activation of alpha2-adrenergic receptors resulted in a fast, voltage-dependent pathway involving Gi/Go G-proteins. This pathway targeted N- and P-type calcium channels The alpha2 modulation was partially reversed by repeated action potential waveforms (APWs). N- and P-type channels have been implicated in synaptic transmission and activation of afterhyperpolarizations in these cells. Our findings suggest that NE can regulate these cellular processes by mechanisms sensitive to spike activity.

Action Potentials↗
PubMed2003

Surgical treatment of multifocal epilepsy involving eloquent cortex.

PURPOSE: This report describes our long-term follow-up for combined resective surgery and multiple subpial transections (MSTs) in patients with refractory epilepsy involving eloquent and noneloquent cortex in multiple lobes. Multiple independent seizure foci made these patients poor candidates for conventional surgery. METHODS: MST and resective surgery were used in 13 patients to treat localization-related refractory epilepsy involving eloquent and noneloquent cortex of two or more lobes. Preoperative investigation was followed by invasive monitoring. RESULTS: Eleven patients had MST plus resection involving two different lobes, and two patients had MST plus resection involving three different lobes. MSTs were performed on the primary sensorimotor cortex (eight patients), temporal language area (two patients), Broca's area (one patient), and on both frontal motor and temporal language areas (two patients). Nine patients had a two-stage procedure, and four patients had a three-stage procedure (two consecutive subdural grid studies followed by resections). Average follow-up was 59.2 months (range, 42-98 months). With a modified Engel Outcome Scale, four patients (31%) had a class I outcome; three (23%), class II; three (23%), class III; and three (23%), class IV. Ten (77%) patients had a >50% reduction of seizure burden. CONCLUSIONS: Combined MST and resection can meaningfully improve seizure control in patients with multifocal epilepsy involving eloquent cortex. Prospective randomized studies are needed.

Adolescent↗
PubMed2005

High-frequency repetitive transcranial magnetic stimulation over the hand area of the primary motor cortex disturbs predictive grip force scaling.

When we repetitively lift an object, our grip force is influenced by the mechanical object properties of the preceding lift, irrespective of whether the subsequent lift is performed with the same hand or the hand opposite to the preceding lift. This study investigates if repetitive high-frequency transcranial magnetic stimulation (rTMS) over the dominant primary motor cortex affects this relationship. After completion of 10 lifts of an object using the dominant hand, rTMS was applied over the dominant primary motor cortex for 20 s. On the first lift following rTMS, the peak grip force was significantly higher than on the lift preceding rTMS. Moreover, this measure remained elevated throughout the following set of lifts after rTMS. rTMS did not change the peak lift force generated by more proximal arm muscles. The same effect was observed when the lifts following rTMS over the dominant motor cortex were performed with the ipsilateral hand. These effects were not observed when subjects rested both hands on their lap or when a sham stimulation was applied for the same period of time. These preliminary data suggest that rTMS over the sensorimotor cortex disturbs predictive grip force planning.

Adult↗
PubMed1998

Exploring the temporal nature of hemodynamic responses of cortical motor areas using functional MRI.

OBJECTIVE: To use functional MRI (fMRI) to study grouped patterns of cerebral activation and the course of hemodynamic responses during performance of two activation tasks (paradigms) using a hand-held joystick to perform movements in a repetitively fixed direction and movements in freely selected random directions. BACKGROUND: Evidence from lesion, electrophysiologic, and functional imaging studies implicates prefrontal and mesial frontal cortex in motor preparation and primary motor cortex in motor execution. fMRI can be used to study cerebral activation and has practical advantages over other methods of functional neuroimaging. METHODS: We acquired 100 multislice T2*-weighted data sets from five healthy volunteers during performance of each paradigm using conventional fMRI. For each paradigm, rest and movement epochs were alternated every 30 seconds. After coregistration and spatial normalization, we combined the data for group studies. We used statistical parametric mapping to compare the early (first 15 seconds) components of the movement epochs with rest as well as the late (last 15 seconds) components of the movement epochs with rest. RESULTS: During the early phase of both paradigms, significant activation was present in rostral and caudal mesial premotor cortex. Right prefrontal cortex was significantly activated during the early component of freely selected joystick movements. Activation of rostral supplementary motor area was maintained during the late component of freely selected movements but decreased during repetitively fixed movements. In contrast, significant activation in contralateral sensorimotor cortex was maintained during both early and late components of both paradigms. CONCLUSIONS: fMRI can detect cortical activation. The temporal resolution of fMRI also allows adaptation of blood oxygenation level-dependent (BOLD) contrast signal to be detected in association cortex. However, the level of BOLD contrast signal in primary motor cortex remained significantly elevated throughout task performance.

Adult↗
PubMed1983

The corticocuneate pathway in the cat: relations among terminal distribution patterns, cytoarchitecture, and single neuron functional properties.

A combined anatomical and physiological strategy was used to investigate the organization of the corticocuneate pathway in the cat. The distribution of the corticocuneate projection was mapped by means of the anterograde horseradish peroxidase (HRP) labeling technique and correlated with the nuclear cytoarchitecture in Nissl and Golgi material, the distribution of retrogradely labeled relay cells after HRP injections in the ventrobasal complex of the thalamus, and the topographic organization derived from single- and multiunit recordings in the decerebrate, unanesthetized cat. This approach provided details about the arrangement of the corticocuneate pathway that were not available from previous studies with anterograde degeneration methods. On the basis of cytoarchitectonic and connectional features, a number of subdivisions are identified in the cuneate nucleus, each of which is associated with characteristic functional properties. In agreement with previous studies, it is found that a large portion of the cuneate nucleus, the middle dorsal part (MCd), is exclusively devoted to the representation of cutaneous receptive fields on the digits. This "core" region contains more thalamic projecting neurons than any other subdivision of the cuneate nucleus. A topographic arrangement also exists in the subdivisions of the rostral cuneate and of the nuclear region ventral to MCd, although in these, receptive fields are larger and predominantly, but not exclusively, related to deep receptors and involve the arm, shoulder, and trunk. Observations on corticocuneate projections were based on injections, mainly focused on functional subdivisions of the primary somatosensory cortex (SI) as described by McKenna et al. (1981). Although cortical projections are mainly to cuneate regions other than its core, a significant proportion of fibers from the region of SI where the digits are represented (particularly area 3b) do project to the MCd region of the cuneate nucleus. Similarly, nuclear areas associated with receptive fields on the arm and trunk are labeled after injection in SI arm and trunk regions, respectively. Thus, a close topographic relationship appears to exist between the somatosensory cortex and cuneate regions related to the same body representation, although nuclear regions in which receptive fields on the neck area are represented receive very sparse or no detectable cortical projections even when the injection of the tracer involves the entire sensorimotor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Long-term consequences of switching handedness: a positron emission tomography study on handwriting in "converted" left-handers.

Until some decades ago, left-handed children who attended German schools were forced to learn to write with their right hand. To explore the long-term consequences of switching handedness, we studied the functional neuroanatomy of handwriting in 11 adult "converted" left-handers and 11 age-matched right-handers. All participants had used exclusively their right hand for writing since early childhood. Using [15O]H2O positron emission tomography, changes in normalized regional cerebral blood flow (rCBF) were assessed while participants repetitively wrote a stereotyped word with their right hand. The kinematics of handwriting did not differ between converted left-handers and right-handers. In innate right-handers, handwriting caused a preponderant left-hemispheric activation of parietal and premotor association areas. In contrast, converted left-handers demonstrated a more bilateral activation pattern with distinct activation foci in the right lateral premotor, parietal, and temporal cortex. Moreover, foci in the right rostral supplementary motor area and the right inferior parietal lobule demonstrated a positive linear relationship between the degree of "left-handedness" and normalized rCBF during right-hand writing. Functional activity in the primary sensorimotor cortex was not affected by handedness. Our findings provide evidence for persisting differences in the functional neuroanatomy of handwriting between right-handers and converted left-handers, despite decades of right-hand writing. Right-hemispheric activation in converted left-handers may reflect suppression of unwanted left-hand movements. Alternatively, this activity may represent persistent left-handedness and, as such, demonstrate a hemispheric asymmetry of hand movement representations in cortical motor association areas in relation to the direction and degree of handedness.

Acoustic Stimulation↗
PubMed1996

Cooperative structures for visually guided reach.

In this introductory commentary, it is argued that the many areas in the cerebral cortex, cerebellum, and elsewhere that are active during reaching movements must interact to generate the appropriate neuronal drive for any given reach trajectory. Cooperative interaction among dispersed neuronal groups may be facilitated by synchronization of intrinsic oscillatory cycles of excitability. In sensorimotor cortex, intervals of oscillatory activity in relatively high frequency bands have been linked to the preparation phase of limb movements. Moreover, synchronization of oscillatory cycles in different loci of frontal and parietal cortex has been reported. Oscillation frequencies change abruptly at the onset of movement, which could reflect altered cerebellar influences on motor thalamocortical circuits. Since relaxation coupling within the thalamus is a probable mechanism of cortical synchronization, it is postulated that cerebellar output contributes to synchronization patterns.

Animals↗
PubMed2004

Structural-functional organization of neurons in the cerebral cortex of rats with different levels of resistance to emotional stress in conditions of exposure to delta sleep-inducing peptide.

Wistar rats with different levels of resistance to emotional stress (ES) were subjected to stress and brain sections stained with Nissl cresyl violet were used for quantitative analysis of the structural organization of neurons in layer V of the sensorimotor cortex. Some animals received delta sleep-inducing peptide (DSIP) 1 h before stress. Control ES-susceptible rats, as compared with resistant rats, had lower levels of normochromic and moderately hypochromic neurons. Normochromic neurons were not seen after stress. Rats susceptible to ES showed particularly sharp decreases in moderately hypo- and hyperchromic neurons, along with increases in the proportions of extremely hypo- and hyperchromic neurons, ghost cells, and ischemically altered cells. After administration of DSIP before stress, ischemically altered cells were not seen in any group: the level of reduction of extremely hyperchromic neurons was smaller in ES-susceptible rats than in ES-resistant rats. It is suggested that brain hypoxia plays a particular role in disorganizing the cortex in conditions of ES, while DSIP has both antistress and antihypoxic properties.

Adaptation, Psychological↗
PubMedDate not supplied

The temporal/spatial evolution of optical signals in human cortex.

Intraoperative measures of functioning brain are an important aspect to understanding normal and diseased cortical response. Previous studies, in animal models, have used optical reflectance maps to illustrate the location and timing of functional activity. We used optical reflectance mapping in patients undergoing parietal tumor resection to reveal the temporal/spatial evolution of perfusion and other related metabolic responses of sensorimotor cortex to peripheral somesthetic stimulation. The somatosensory cortex of seven anesthetized patients was mapped in response to transcutaneous electrical median and ulnar nerve stimulation using optical reflectance imaging. The time course and spatial extent of this response were measured and correlated with evoked potential maps collected during the same conditions. Observable signals first appeared within 1-2 sec, peaked at 3 sec, and disappeared by 9 sec. These signals colocalized with the largest evoked potentials in both the sensory and motor regions and demonstrated topological specificity with median and ulnar nerve stimulation. Maps of this temporal/spatial resolution illustrate the integrative and dynamic nature of the neuronal, vascular, and metabolic responses of human cortex. These data also provide insight to the mechanisms responsible for signals obtained using other brain imaging techniques such as PET and fMRI.

Brain Mapping↗
PubMed2002

Functional MRI evidence for motor cortex reorganization adjacent to a lesion in a primary motor cortex.

OBJECTIVE: The object of this study was to verify motor cortex reorganization in patients with primary motor cortex injury using functional magnetic resonance imaging. DESIGN: Ten control subjects and two patients with primary motor cortex injury, caused by a traumatic brain injury in patient 1 and meningioma in patient 2, were evaluated. Functional magnetic resonance imaging was performed using the blood oxygenation level-dependent technique at 1.5 T with hand movements. RESULTS: The contralateral primary sensorimotor cortex was activated by unaffected hand movements. However, only the contralateral primary sensory cortex in patient 1 and the premotor area in patient 2 were activated by affected hand movements, which were totally absent in control subjects. CONCLUSION: We believe that the hand motor function of injured primary motor cortex was shifted into the primary sensory cortex in patient 1 and premotor area in patient 2. In conclusion, this finding may reflect a functional reorganization of the motor area in patients with a primary motor cortex injury.

Adult↗
PubMedDate not supplied

[Functional role of the red nucleus in the cerebral cortex-cerebellum-spinal cord communication system].

Unilateral transection of the rubrospinal tract before lesion of the red nucleus or the ventrolateral thalamic nucleus has been shown to facilitate recovery of operantly conditioned reflexes and compensatory processes in rats. Such strengthening of the recovery plasticity and operantly conditioned was found when transection of the bulbar pyramide performed before ablation of the sensorimotor cortex. These influences are explained by activation of the rubroolivary projection, which is switching of descending cortico-rubrospinal system on the corticospinal system, and on the contrary. The general property of this phenomenon is that preliminary lesion of the peripheral part of the descending spinal projection to acquire a signal forestalling significance for mibilization of compensatory brain capacity in order to recovery the deficit of central link of the system.

Animals↗
PubMed2005

An fMRI study of the motor system in patients with neuropsychiatric systemic lupus erythematosus.

Functional cortical changes have been demonstrated in patients with several neurological conditions, including stroke, tumors and MS. The correlation found between the extent of fMRI activations and the extent and severity of brain structural damage suggests an adaptive role of these functional changes. In this study, we assess, using fMRI, the brain pattern of movement-associated cortical activations in neuropsychiatric systemic lupus erythematosus (NPSLE) patients and investigate whether the extent of cortical reorganization is associated with the extent of brain pathology, measured on dual-echo and diffusion tensor (DT) MR images. From 14 right-handed NPSLE patients and 14 matched controls, we obtained: (a) fMRI during the performance of repetitive flexion-extension of the last four fingers of the right hand; (b) dual-echo and (c) pulsed-gradient spin-echo echo-planar sequence to calculate DT MRI maps of the normal-appearing white (NAWM) and gray (NAGM) matter. Brain T2-visible abnormalities were detected in 11 NPSLE patients. Compared with controls, NPSLE patients had significantly higher NAWM fractional anisotropy histogram peak height (P = 0.005), and more significant activations of the contralateral primary sensorimotor cortex, putamen and dentate nucleus. They also had more significant activations of several regions located in the frontal and parietal lobes as well as of MT/V5 and the middle occipital gyrus, bilaterally. Strong correlations (r values ranging from 0.79 to 0.87) were found between relative activations of sensorimotor areas and the extent and severity of brain damage. Movement-associated functional cortical changes do occur in patients with NPSLE and might contribute to the maintenance of their normal functional capacities.

Adult↗
PubMed1990

Axotomized, adult basal forebrain neurons can innervate fetal frontal cortex grafts: a double fluorescent tracer study in the rat.

The ability of axonal regeneration of identified adult basal forebrain (BFB) neurons was examined after homotopic grafting of fetal neocortical tissue to a lesion cavity in the frontal neocortex. Using a four step experimental procedure, adult rats first received an injection of the fluorescent dye Fluoro-Gold (FG) into the sensorimotor cortex in order to label those neurons with projections to the area by retrograde axonal transport. After one week the injection area was removed by aspiration, leaving a cavity in the neocortex. One week later a block of fetal (E14) frontal cortical tissue was placed in the cavity. The animals were then allowed to survive for 6 weeks before a second fluorescent tracer, Nuclear Yellow (NY), was injected into the transplant. The animals were sacrificed 24 h later and analyzed by fluorescence microscopy. Both single labeled, FG and NY containing neurons and double labeled neurons containing both tracers were found in the BFB. The results demonstrate that adult BFB neurons can reestablish cortical projections into fetal cortical grafts (double labeled neurons), and they suggest that other BFB neurons, not initially innervating the lesioned cortical area, have sprouted into the transplant (NY labeled neurons).

Animals↗
PubMed1982

Changes in the excitability of rat cerebral cortex after a self-sustained after-discharge.

Changes in the duration of the cortical self-sustained after-discharge (SSAD) were studied in relation to the preceding SSAD in adult rats. An "excitability cycle" could be constructed by means of different intervals between the end of the first SSAD and the beginning of subsequent electrical stimulation of the sensorimotor cortex. During short intervals (30, 60 and 120 sec) the second SSAD was significantly shorter than the first. No significant differences were found with intervals of 3 and 5 min; all longer intervals, except 120 min, resulted in significant prolongation of the second SSAD. The possibility of elicitation of the second SSAD also increased with increasing intervals, demonstrating thus the presence of a "refractory period." The results with manifold stimulation demonstrated the rather complicated nature of the changes of excitability during post-ictal periods.

Animals↗
PubMedDate not supplied

Localized echo-volume imaging methods for functional MRI.

To perform true three-dimensional activation experiments in the human brain, dedicated localized echo-volume imaging (L-EVI) methods were developed. Three-dimensional acquisition allows generation of activation maps with minimal vascular enhancement related to inflow effects. The rapid acquisition of the L-EVI (approximately 100 msec) reduces signal instabilities caused by motion, facilitating the detection of the small intensity changes expected with brain activation. Single-shot L-EVI was performed on normal volunteers at 1.5 T, imaging a three-dimensional predefined volume (240 x 45 x 45 mm3) in the superior portion of the brain with a spatial resolution of 3.75 x 5 x 5 mm3. Increased brain coverage was achieved with a multi-volume imaging (three-shot) version, which simultaneously achieved effective suppression of signals from cerebrospinal fluid. In addition, both asymmetric spin-echo (ASE) and spin-echo (SE) versions of the technique were used to detect blood oxygenation level dependent (BOLD) signal changes in the motor cortex with a finger-tapping paradigm. Images obtained by the L-EVI sequence were qualitatively comparable to standard multislice two-dimensional echo-planar images. Both ASE and SE functional MRI (fMRI) experiments showed consistent activation in the contralateral primary sensorimotor cortex. Furthermore, significant differences in location and magnitude of activation was observed between the two methods, confirming theoretical predictions.

Brain Mapping↗